This invention relates to void closures used in a bottomless trench duct in an underfloor wire distribution system.
The underfloor wiring system is comprised of a cellular subfloor deck assembly through which electrical and communication wires are channeled. Generally, the cellular subfloor deck consists of a base wall and a corrugated upper wall having a plurality of crests and troughs. The base wall need not be continuous, but may be discontinuous to define predetermined raceway cells with the corrugated upper wall. Overlying the cellular subfloor at right angles to the raceway cells are one or more bottomless trench ducts, the top walls of which are provided with removable access cover plates. The electrical and communication wires are strung through the trench duct and access openings are provided in predetermined raceway cells so that the wires may be branched into the raceways for communication with electrical and communication terminals and connectors.
Underfloor trench ducts for wiring systems are frequently used in buildings where many electrical and communication outlets are required. Some typical examples of trench ducts are disclosed in the following U.S. Pat. Nos.: 3,435,568; 3,453,791; 3,721,051; and 3,593,472.
In forming a bottomless trench duct, the problem encountered is to keep the concrete from flowing into the trough in the cellular subfloor below the side rails of the trench duct. In the past, the troughs have been blocked off by means of plugs disposed under the sidewall of the trench duct or the inner sidewall of the trench duct has been formed with vertically downwardly extending portions to block off the trough, as is disclosed in U.S. Pat. No. 3,721,051.
The plugging method of blocking the trough is unsatisfactory because the plug may become dislodged and move out of position while the concrete is being poured. The alternative method of cutting downwardly extending projections on the inner sidewalls of the trench duct is unsatisfactory because the troughs are not of uniform shape and spacing, and in order to accommodate the various irregular spacings and configurations of the trough, the projections on the sidewalls must be precut or stamped in small sections. This operation requires the use of many different dies, and results in the need for many end welds on the short side rail sections.